U.S. patent number 3,739,282 [Application Number 05/096,901] was granted by the patent office on 1973-06-12 for radio receiver for single sideband reception.
This patent grant is currently assigned to Licentia Patentverwaltungs-G.m.b.H.. Invention is credited to Walter Bruch, Werner Scholz.
United States Patent |
3,739,282 |
Bruch , et al. |
June 12, 1973 |
RADIO RECEIVER FOR SINGLE SIDEBAND RECEPTION
Abstract
In a single sideband radio receiver for the selective reception
of signals transmitted by a plurality of transmitters at equal
frequency spacing (.DELTA.f.sub.s) the local oscillator in the
receiver, which may produce voltages for either heterodyning or
demodulating the received signal, is controlled by means of an
arrangement including an ultrasonic delay line which serves as the
frequency standard for the spacing of the local oscillator
frequencies (.DELTA.f.sub.o) so that it locks in and oscillates
only at defined oscillator frequencies corresponding to the
frequencies of the transmitters. Various alternative embodiments of
controlling the local oscillator in this manner are disclosed.
Inventors: |
Bruch; Walter (Hannover,
DT), Scholz; Werner (Hannover, DT) |
Assignee: |
Licentia
Patentverwaltungs-G.m.b.H. (Frankfurt am Main,
DT)
|
Family
ID: |
5753591 |
Appl.
No.: |
05/096,901 |
Filed: |
December 10, 1970 |
Foreign Application Priority Data
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Dec 11, 1969 [DT] |
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P 19 62 156.8 |
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Current U.S.
Class: |
455/199.1;
329/357; 329/358; 455/324 |
Current CPC
Class: |
H04B
1/302 (20130101) |
Current International
Class: |
H04B
1/30 (20060101); H04b 001/68 () |
Field of
Search: |
;331/172-174
;325/50,330,419,420 ;329/50,122 ;179/15FS ;332/45 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Mayer; Albert J.
Claims
We claim:
1. In a radio receiver for the selective reception of single
sideband signals (f.sub.s) transmitted by a plurality of
transmitters at equal frequency spacing (.DELTA.f.sub.s) including
a frequency selective amplifier for receiving the transmitted
signals, a local oscillator, which is tunable in synchronism with
said amplifier, for producing output signals having defined
frequencies at a frequency spacing (.DELTA.f.sub.o) equal to n or
1/n times the frequency spacing (.DELTA.f.sub.s) of the transmitter
frequencies, where n is a whole number (1, 2, 3 . . .) and means
for combining the received signal and the output signal from said
local oscillator to detect the received signal, the improvement
comprising: means, including an ultrasonic delay line whose delay
time (.tau.) is equal to the reciprocal value of the spacing of the
oscillator frequencies (.DELTA.f.sub.o) and which serves as the
frequency standard for the spacing of the local oscillator
frequencies (.DELTA.f.sub.o), for controlling the frequency of said
local oscillator so that it locks in and oscillates at only said
defined frequencies.
2. The radio receiver as defined in claim 1 wherein said means for
controlling the frequency of said local oscillator comprises: a
generator means for producing an output pulse train having a
frequency which is equal to the spacing of the oscillator
frequencies (.DELTA.f.sub.o), said ultrasonic delay line being the
frequency determining member of said pulse generator; and means for
coupling said output pulse train to a frequency controlling input
of said local oscillator.
3. The radio receiver as defined in claim 2 wherein said coupling
means comprises means for directly feeding said pulse train to said
local oscillator to synchronize said local oscillator to the
selected oscillator frequency by a direct locking action.
4. The radio receiver as defined in claim 2 wherein said coupling
means further includes a phase comparison means for comparing said
pulse train and the output signal of said local oscillator and for
producing an output voltage which is coupled to said local
oscillator and acts as a control voltage on the frequency of said
oscillator.
5. The radio receiver as defined in claim 2 wherein said coupling
means includes means responsive to said pulse train for producing
oscillations of the order of magnitude of a local oscillator
frequency, which oscillations are interrupted at frequency
intervals corresponding to said frequency spacing
(.DELTA.f.sub.o).
6. The radio receiver as defined in claim 5 wherein said means
responsive to said pulse train comprises a start-stop oscillator
which is actuated by each of the pulses of said pulse train to
generate a number of oscillations at a local oscillator
frequency.
7. The radio receiver as defined in claim 5 wherein said coupling
means further includes a phase comparison means for comparing the
phase of said interrupted oscillations and the output signal of
said local oscillator and for providing an output voltage which is
coupled to said local oscillator and serves as the control voltage
(U.sub.R) for controlling the frequency of said local
oscillator.
8. The radio receiver as defined in claim 1 wherein said means for
controlling the frequency of said local oscillator comprises said
ultrasonic delay line which is disposed in the feedback path of
said local oscillator.
9. The radio receiver as defined in claim 1 wherein said means for
controlling the frequency of said local oscillator comprises said
ultrasonic delay line which is connected between the output and a
synchronizing input of said local oscillator to provide direct
locking synchronization thereof.
10. The radio receiver as defined in claim 1 wherein said
ultrasonic delay line has its input connected to the output of said
local oscillator and wherein said means for controlling the
frequency of said local oscillator further includes means for
comparing the phase of the input and output signals of said
ultrasonic delay line to provide an output voltage which is coupled
to said local oscillator and serves to control the frequency
thereof.
11. The radio receiver as defined in claim 1 wherein said
ultrasonic delay line is a PAL delay line with a delay time (.tau.)
which is adapted to the frequency spacing (.DELTA.f.sub.o) of the
oscillator frequencies (f.sub.o).
Description
BACKGROUND OF THE INVENTION
The present invention relates to a radio receiver for single
sideband reception, and particularly a circuit for producing an
accurate frequency pattern for an oscillator serving for
heterodyning or demodulating the received signal.
In radio receivers for single sideband reception, it is known
(Rundfunktechnische Mitteilungen 1969, No. 2, pages 53-57) to
employ a quartz oscillator, a frequency divider and a pulse stage
to produce a carrier frequency spectrum which has spectral lines
for the individual transmitting frequencies which serve as
additional carriers in order to provide for the distortion free
demodulation of the single sideband signals. In such receivers, the
selectivity of the transmitter frequency is realized before the
demodulator by a known selective tuning circuit. Thus signals must
be produced in the receiver which have frequencies associated with
the transmitting frequencies.
It is also known (Rundfunktechnische Mitteilungen, 1967, No. 6,
pages 304-313) to convert the received single sideband signal in a
mixer stage to an IF signal of constant frequency by utilizing a
heterodyning oscillator which is so controlled by a pulse train
having a frequency equal to the frequency spacing of the
transmitter that it locks in only at the frequencies assigned to
the transmitter frequencies.
Thus, in both cases, a local oscillator is required in the receiver
which only oscillates at certain frequencies which are assigned as
transmitting frequencies and which lie at the frequency spacing of
the transmitters to be received. The frequency standard for this
frequency spacing is determined, for example, by a quartz filter or
by two of these received transmitters. These circuits are
relatively complicated because they require frequency divider or
control circuits.
SUMMARY OF THE INVENTION
It is the object of the present invention to simplify the circuit
for producing the accurate frequency pattern of the local
oscillator in the receiver and to realize high accuracy of the
frequency spacing of the generated oscillator frequencies.
This is accomplished according to the present invention in that the
local oscillator in the single sideband receiver, which oscillator
may produce signals utilized either for heterodyning or
demodulating the received signals, is controlled by means of a
circuit, including an ultrasonic delay line which serves as the
frequency standard for the spacing of the oscillator frequencies
(.DELTA.f.sub.o), so that the oscillator locks in and oscillates
only at the frequencies associated with the frequencies (f.sub.s)
of each of the transmitters which are equally spaced at a spacing
.DELTA.f.sub.s.
A number of different embodiments for controlling the local
oscillator in this manner are disclosed. For example, according to
a number of embodiments, the delay line forms the frequency
determining member of a pulse train generator whose output pulses
either directly or indirectly, e.g., by means of a phase comparator
output signal, controls the frequency of the local oscillator.
According to other embodiments of the invention, the desired
control of the oscillator is achieved by connecting the delay line
in the feedback path of the oscillator, or between the output and a
synchronizing input of the oscillator.
According to still a further embodiment of the invention, the input
of the delay line is connected to the output of the local
oscillator a control signal for the oscillator is generated in a
phase comparator which compares the phase of the input and output
signals from the delay line.
The present invention is based on the realization that ultrasonic
delay lines which are known for other purposes can be used with
particular advantage in the above-mentioned single sideband
receiver. Such a delay line constitutes not only a relatively small
component which is not subject to malfunction, but additionally,
since such delay lines are currently being manufactured in large
numbers for color television receivers, the price is also tenable.
Moreover, such a delay line represents a particularly accurate
frequency standard because its delay time is extraordinarily
stable, can be set very accurately and is practically independent
of temperature fluctuations. For example, a so-called PAL delay
line i.e., the ultrasonic delay line commonly used in PAL type
color television receiver can be used since its delay time is
adapted to the respective frequency spacing. The delay time of a
PAL delay line lies in the order of magnitude of the reciprocal
value of the transmitter frequency spacing in the medium frequency
range. The pass frequency of such a PAL line also lies in the order
of magnitude of the transmitter frequencies used for single
sideband reception. The present invention thus opens a new field of
application for the known ultrasonic delay line.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a basic circuit diagram of a selective single sideband
receiver constructed according to the present invention.
FIG. 2 illustrates the frequency spectrum of the received and local
oscillator signals for explaining FIG. 1.
FIGS. 3-8 show various alternative circuit embodiments for
controlling the receiver local oscillator using a delay line
according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to FIG. 1, there is shown a single sideband receiver
wherein, in a conventional manner, a high frequency signal
modulated in the single sideband is received by an antenna 1,
amplified in a selective tunable amplifier 2 and fed to a mixer or
detector stage 3 whose output voltage is fed via an IF amplifier 4,
to a demodulator or detector 5 which furnishes a low frequency
signal (NF), e.g., an audio signal, at an output terminal 6. The
mixer stage 3 is controlled by a controllable heterodyning
oscillator 7 (local oscillator) in a well-known manner so that the
amplifier 4 receives an intermediate frequency (IF) of constant
frequency. At the output of amplifier 4 the carrier frequency is
filtered out of the IF signal by means of a narrow band filter 8,
which may, e.g., be a quartz filter, a ceramic filter or a
multistage filter with concentrated components, as a singular
frequency and is fed to demodulator 5 via amplifier 9 and line 10
to be demodulated without distortion.
As illustrated in FIG. 2a, the antenna receives signals from a
plurality of transmitters which signals are at a frequency spacing
of .DELTA.f.sub.s (e.g., 9 kHz) at frequencies f.sub.s1, f.sub.s2 .
. . The oscillator 7 is tuned to the individual transmitters in
synchronism with amplifier 2 so that it produces the oscillator
frequency f.sub.o1 for transmitter frequency f.sub.s1, which
frequency f.sub.01 is shifted by the intermediate frequency (e.g.,
460 kHz) with respect to f.sub.s1. According to the present
invention, the oscillator 7 is controlled by a circuit 11
containing an ultrasonic delay line 12 in such a manner that it
oscillates only at the oscillator frequencies f.sub.o assigned to
the transmitter frequencies f.sub.s, i.e., oscillator 7 locks in
only at these assigned frequencies and does not oscillate between
these frequencies. This high accuracy of the oscillator frequency
is necessary because the frequency of the carrier must be
particularly accurate in the intermediate frequency path so that it
falls in the very narrow passing range of the bandpass filter 8. To
accurately produce the desired frequency pattern of the oscillator
frequencies (FIG. 2b) the delay line 12 is provided. The delay time
of delay line 12 is selected to be equal to, for example, the
reciprocal value of the frequency spacing .DELTA.f.sub.s and thus
determines the spacing .DELTA.f.sub.o of the oscillator frequencies
f.sub.o. It is to be understood that although in FIG. 1 the
oscillator 7 is a heterodyning oscillator (local oscillator), the
invention is equally applicable to use with a local oscillator
which provides carrier frequency oscillations and whose output is
fed to demodulator 5 over line 10, which is formed in FIG. 1 by
members 8, 9, if no conversion to the intermediate frequency occurs
before the demodulation and demodulator 5 directly receives the
different transmitter frequencies. Additionally, if required, the
delay time .tau. and thus the frequency spacing .DELTA.f.sub.o may
be varied, or made adjustable, by an additional delay line in
series with delay line 12, which additional line may be
adjustable.
With the aid of several alternative circuit embodiments of the
invention, it will now be explained how the oscillator 7 is
controlled by means of the delay line 12 so that it oscillates only
at the frequencies f.sub.o which lie at spacings
.DELTA.f.sub.o.
As shown in FIG. 3, the control circuit 11 comprises a control
generator 11' which generates pulses 14 at frequency
.DELTA.f.sub.o. The delay line 12 which determines the frequency of
the pulses 14 is provided with a delay time .tau. equal to
1/.DELTA.f.sub.o. With the oscillator 7 oscillating at one of
frequencies f.sub.o, pulses 14 control oscillator 7 with a direct
locking action so that the oscillator oscillation 15 exhibits, for
example, a zero passage at each pulse 14. Between two pulses 14
there is thus always a whole number of oscillator oscillations 15.
This means that the frequency of oscillations 15 is always a whole
number multiple of frequency .DELTA.f.sub.o which in turn means
then that oscillator 7 can oscillate only at whole number multiples
of .DELTA.f.sub.o. Thus a frequency spectrum according to FIG. 2b
results when the oscillator is turned over its full range.
According to the embodiment of FIG. 4 the synchronization of the
oscillator 7 by means of the output pulses 14 of generator 11' does
not occur with a direct locking action as in FIG. 3 but rather via
a control signal U.sub.R generated by a phase comparison stage 16.
As illustrated, stage 16 compares the phase position of a pulse 14
with the oblique edge of the sine voltage output 15 of oscillator 7
during zero passage and furnishes the control voltage U.sub.R
proportional to the difference. This control voltage U.sub.R is fed
to the oscillator 7 to control the oscillator frequency or phase,
in a well-known manner, so that the zero passages of oscillation 15
always coincide with pulses 14, whereby the above-mentioned
requirement for the frequency spectrum of the output oscillations
of oscillator 7 is also met.
In the embodiment of the invention shown in FIG. 5, the output
pulses 14 of control circuit 11 control a start stop oscillator 17
which generates several oscillations 18 at one of the oscillator
frequencies f.sub.o, e.g., at a frequency f.sub.o in the center of
the total frequency band covered by oscillator 7, in response to
each pulse 14. Since these oscillations 18 are interrupted at
frequency spacing .DELTA.f.sub.o, they represent a frequency
spectrum as shown in FIG. 2b. A discriminator 16 is provided which
compares the oscillations 18 with the oscillations of oscillator 7
and again produces a control voltage U.sub.R which controls the
oscillator 7, depending on its tuning, to one of frequencies
f.sub.o. When the oscillator is fully tuned, it also locks on one
of frequencies f.sub.o as shown in FIG. 2b.
According to the embodiment of FIG. 6, instead of controlling an
oscillator by means of pulses at a desired frequency, the
oscillator 7 is formed by a tunable selective amplifier 19 between
whose output and input the delay line 12 is disposed. The delay
line 12 thus forms a feedback path for amplifier 19 thus providing
the required phase shift so that the amplifier 19 and acts as an
oscillator. The feedback condition for the generated oscillation 15
is met only when the frequency of the oscillation is a multiple of
the value 11.tau. of the delay line 12. The oscillator 7 formed by
delay line 12 and amplifier 19 can thus oscillate only at
frequencies which are whole number multiples of .DELTA.f.sub.o, so
that the spectrum according to FIG. 2b is again assured. The
particular multiple of .DELTA.f.sub.o at which the oscillator 7
oscillates is determined by the tuning of amplifier 19 which is
again in synchronism with the transmitter tuning according to FIG.
1.
In FIG. 7, which is a modification of FIG. 6, the delay line 12 is
disposed between the output and an input of an oscillator 7 and
serves to synchronize the locking thereof. Oscillator 7, without
delay line 12, is self-oscillating and would thus, as is
conventional, continuously change its frequency during tuning. With
the locking synchronization provided via delay line 12 and line 20
it is assured that the oscillator 7 can oscillate only when the
voltage across line 20 effects a synchronization with the phase of
the generated voltage. This again is the case only, as in FIG. 6,
at certain frequencies given by the delay time and disposed at a
spacing 1/.tau.. During tuning the oscillator 7 thus again
oscillates only at these frequencies according to FIG. 2b.
In the embodiment of FIG. 8 the output voltage of the tunable
oscillator 7 is fed to the input of delay line 12 and the input
voltage and output voltage of the delay line 12 are fed to the
phase comparison stage 16 whose output control voltage U.sub.R is
again utilized to control the oscillator 7. The control voltage
U.sub.R insures that the voltage at the input and output of the
delay line 12 has a defined phase relationship, e.g., the same
phase. However, the identical phase can be given only at certain
frequencies of the output voltage of oscillator 7, i.e., whenever
the delay time .tau. is a whole number multiple of the period
duration of the frequency. Thus, oscillator 7 can oscillate only at
frequencies which are offset with respect to one another by the
spacing .DELTA.f.sub.o = 11.tau. . Consequently, only certain
frequencies according to FIG. 2b result again at terminal 13 during
tuning.
Oscillator 7 may additionally be automatically frequency controlled
by a known circuit (the so-called automatic fine tuning). This
subsequent tuning voltage is generated, for example in a phase
discriminator fed with the IF voltage and takes care that the
intermediate frequency always has its rated value. In the circuit
according to FIG. 1 this control circuit would insure, for example,
that the intermediate frequency always falls exactly in the passing
range of quartz filter 8.
It will be understood that the above description of the present
invention is susceptible to various modifications, changes and
adaptations, and the same are intended to be comprehended within
the meaning and range of equivalents of the appended claims.
* * * * *